This invention relates to a control apparatus for elevators, and more particularly to an elevator control apparatus which generates a terminal floor deceleration command signal.
A prior art elevator control apparatus will be described with reference to FIGS. 1-4.
FIG. 1 shows a diagram of the overall elevator control apparatus, and concerns the prior-art apparatus and the apparatus of the present invention. Numeral 1 designates a cage, and numeral 2 a counterweight. A rope 3 is wound round a sheave 4, and the cage 1 and the counterweight 2 are respectively suspended from one end and the other end of the rope 3. Numeral 5 indicates an induction motor which drives the sheave 4, numeral 6 a pulse generator which generates pulses proportional to the movement distance of the cage 1 on the basis of the rotation of the motor 5, numeral 7 a counter circuit which counts the pulses from the pulse generator 6, and numeral 8 a microcomputer system which receives the pulse count value 7a of the counter circuit 7 to calculate a residual distance by way of example. Shown at numeral 9 is a three-phase A.C. power source. Numeral 10 indicates a power conversion device which converts three-phase alternating current into electric power suitable for the speed control of the elevator, and to which a command signal 8a from the microcomputer system 8 is applied thereby to control the torque and rotational frequency of the motor 5. Numeral 11 denotes the plane of a terminal floor, and numeral 12 a cam mounted on the cage 1. A terminal position detector 13 is disposed in a hoistway, and an output signal 13a delivered therefrom is input to the microcomputer system 8.
FIG. 2 shows the details of the microcomputer system 8. This microcomputer system comprises first and second microcomputers 80 and 90. The first microcomputer 80 includes a CPU 81, a ROM 83, a RAM 84, an input port 85, and an output port 86 which the connected to each other through a bus 82. The input port 85 is supplied with the pulse count value 7a of the counter circuit 7. The microcomputer 80 thus arranged performs the running control and sequence control of the cage 1, and generates a normal speed command signal V.sub.N being the ordinary speed command signal of the cage 1. The normal speed command signal V.sub.N has a relation of V.sub.N =.sqroot.2.beta..sub.A R.sub.A at a constant deceleration .beta..sub.A in correspondence with a residual distance R.sub.A to a scheduled arrival floor. In addition, the residual distance R.sub.A is calculated on the basis of the pulse count value 7a of the counter circuit 7.
Similar to the first microcomputer 80, the second microcomputer 90 includes a CPU 91, a ROM 93, a RAM 94, an input port 95, and an output port 96, all connected to each other through a bus 92. The input port 95 is supplied with the pulse count value 7a of the counter circuit 7 and the output signal 13a of the terminal position detector 13. The second microcomputer 90 thus arranged generates a command signal 8a for controlling the rotational frequency and torque of the motor 5 This command signal 8a is delivered from the output port 96 to the power conversion device 10.
When, when the cage 1 has approached the terminal floor, the second microcomputer 90 receives the output signal 13a of the terminal position detector 13 and sets a residual distance R.sub.B. Thenceforth, it calculates the residual distance R.sub.B on the basis of the pulse count value 7a of the counter circuit 7. On the basis of this residual distance R.sub.B, a terminal-floor slowdown command signal V.sub.S is calculated in accordance with V.sub.S =.sqroot.2.beta..sub.B R.sub.B. .beta..sub.B is a constant deceleration in accordance with the residual distance R.sub.B and is greater than .beta..sub.A.
The normal speed command signal V.sub.N calculated by the first microcomputer 80 is fed into the CPU 91 of the second microcomputer 90 through a transmission interface 100 which connects the respective CPU's 81 and 91 of the first and second microcomputers. The command signal V.sub.N and the terminal-floor slowdown signal V.sub.S are compared in the CPU 91, and the smaller one is used as the final speed command signal. On the basis of this speed command signal, the command signal 8a for the power conversion device 10 is delivered through the output port 96.
Owing to the control apparatus for such a construction, even when the normal speed command signal V.sub.N has not lowered due to any abnormality in spite of the approach of the cage 1 to the terminal floor 11, the cage 1 can be safely decelerated by the terminal-floor slowdown command signal V.sub.S so as to arrive at the terminal floor.
FIG. 3 is a diagram in which the relationship between the normal speed command signal V.sub.N calculated by the first microcompuer 80 and the terminal-floor slowdown command signal V.sub.S calculated by the second microcomputer 90 is expressed in correspondence with the residual distances R.sub.A and R.sub.B. As seen in FIG. 3, V.sub.N decreases at the constant deceleration .beta..sub.A, and V.sub.S decreases at the constant deceleration .beta..sub.B. In addition, V.sub.N and V.sub.S become very close for small values of the residual distances.
In this regard, the microcomputers 80 and 90 usually have unequal calculation cycles, and the installation error of the terminal position detector 13 and the response delay thereof are involved, so that the residual distances R.sub.A and R.sub.B become R.sub.A .noteq.R.sub.B.
Near the level of the terminal floor, accordingly, N.sub.N &gt;V.sub.S can occur as shown in FIG. 4 on account of the difference of the calculating cycles, etc., and the terminal-floor showdown command signal V.sub.S is selected in spite of the normal speed command signal V.sub.N being correct. This has led to the problems that comfort in ride becomes worse near the levels of the terminal floors than at intermediate floors, and that the accuracies of floor arrival worsen.